N-acetylcysteine, or NAC, is a nutritional supplement with antioxidant and anti-inflammatory properties. After ingestion, N-acetylcysteine is metabolized into glutathione, a key antioxidant with effects throughout the body. In the lungs, glutathione deficiency (common in alcoholics) is linked to a higher risk for ARDS. People with COPD and smokers without COPD tend to have lower glutathione levels, which correlate with worse lung function."